05/14/2020
DU Services: Building best practices memo
Building Operations Best Practices for 2020 and beyond
Today everyone is trying to respond to a new normal considering the Covid-19 Pandemic. On top of all the financial challenges the lock downs have imposed, now we are trying to get back to work and answer the question “is our building safe”.
The real answer is not as straight forward as we would all like. ASHRAE (American Society of Heating, Refrigeration and Air Conditioning Engineers) was founded in 1959 and is devoted to the advancement of Indoor Air Quality and providing technical standards and guidelines. The have teams working on Best Practices for building owners and operators. The teams are made up of industry professionals, engineers, scientists and professors. The common theme is of all the strategies, there is no magic bullet. Every building has unique challenges and the overall strategy should include multiple solutions for the best results.
The ASHRAE Position Document on Infectious Aerosols outlines HVAC-system
recommendations for various buildings and facilities which are aimed at reducing
occupant exposure to airborne disease. Practices addressed include ventilation-related
strategies comprised of dilution, airflow patterns, pressurization, temperature and
humidity distribution and control, filtration, and other “best practice” approaches.
Here are some of the of the recommendations and standards they are working on:
Mechanical filtration upgrades.
Increased Outside Air intake
Proper humidity design & control.
UVGI systems for coil, in-duct, and upper room use. (Ultraviolet Lights)
Air ionization & other advanced IAQ technologies. (control odors, kill bacteria and viruses, improve filter efficiency)
Ozone considerations, concerns, and regulations. (new recommendations for zero ozone emissions)
So, what does all this mean to you? I will try to break it down one piece at time.
Filtration:
The industry standard for Office and Non-Medical has always been MERV-8 filters. What is MERV-8 you are asking. The MERV rating is the size of particles that will be trapped. Anything smaller will pass through. The chart below helps explain.
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By going to a higher MERV filter starting at MERV-13 you begin to trap bacteria and smoke. When you get to MERV-17 you begin to catch viruses. Problem solved, just put in the higher filter, right?
Not so fast. Not all equipment is created equal and with every plus there is a minus. The higher the filtration, the more fan and energy is required to move the same amonunt of air. A MERV-13 filter in a standard Roof Top Unit designed for a MERV-8 will lose around 7% of its airflow. Depending on the unit, its criticality and excess capacity it may work or it may fall below an acceptable level of functionality. We need to evaluate each system individually.
Price: A MERV-13 is up to 4 time the cost of a MERV-8. While at first blush it’s huge, depending on your site it may not be that impactful. Critical systems may require re-balancing the air to maintain system performance.
It is also important to make sure we use proper PPE for all Filter Changes. These include Safety Glasses, Face Mask, Gloves and bagging all used filters to avoid spreading any contaminents back into the space. Gloves should be changed frequently.
Another consideration is how to address Fan Coil Units and Heat Pumps with small fans. If the unit doesn’t have a High Static option we may need to over size the filter i.e. use a 4” instead of a 2” to maintain airflow. These filters come at a high cost and may require re-balancing the system after installation to maintain system performance
We are happy to evaluate your specific equipment and make recommendations and give you the options available at this time.
*Please note that the MERV-13 filters are in high demand and curently averaging a 3 week lead time.
Increased Outside Air:
Another recommendation is increasing the percentage of Outside Air up to 100%. This solution has several impacts to the equipment operation. Not all, or many systems are designed to bring in 100% outside air under all conditions. In the heat of summer or the cold of winter, special provisions are required to bring the air to the required temperature. Secondly is the operational cost. The more heating or cooling required consumes large amounts of energy. Third is tennent comfort. Standard equipment does not have all the controls or staging required to avoid temperature swings in the discharge air and can cause a negative effect on comfort.
That being said we can look at incrementally raising the outside air to the maximum for each piece of equipment.
Humidity and Temperature:
There is some evidence suggesting that between 40% and 50% humidity is the best for controlling viruses.
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I have read conflicting opinions on this and most facilities lack the equipment to control humidity in our dry environment. It would be different in an area where you are trying to lower the humidity. I am going to keep researching this but it isn’t a practical solution for most.
Ultraviolet Lights:
Ultraviolet Lights or UV by itself is considered a passive Air Purification system in that it treats the air conditioning coil or duct and some of the air stream but stops there. The return air carries some contaminants to the light but the space itself is not directly treated.
Air Ionization and Advanced Technologies:
These technologies are unique in that they Ionize the air which causes many small particles to stick together and allow them to “get bigger” and filtered out. This is the same way an Electrostatic Air Cleaner works. It is not uncommon to have to increase filter change frequencies as the filters are catching more particulates that would have passed through a standard filter.
Additionally, some brands use Photoreactive metals and others rely solely on the ionization process. Both technologies claim equal effectiveness and have case studies to back them up. This is not new to the industry and have been successfully installed for many years for dust, odor and viruses/Bacteria control.
These units are available in many sizes and configurations ranging from PTAC units, Ductless Mini Splits, Fan Coils, Heat Pumps, Roof Top Units and Central Station Air Handlers.
Ozone Emissions:
Ozone is largely considered to be an irritant and discouraged as a solution for the mitigation of Molds, Bacteria and Viruses. Standards are moving towards units certified as “Zero Ozone Emissions”. This should be a consideration moving forward.
Conclusions:
In conclusion, there is no magic bullet, one size fits all solution for Indoor Air Quality and Covid 19 control. The truth is there never was, only increased scrutiny and awareness. The Best Practices that you chose need to be applied to your individual building and tailored for all conditions including Occupancy, Density Equipment capacity. The chart below shows the effectiveness of various strategies from least effective on the bottom to most effective on the top. No single thing, rather combinations of different strategies are considered the most effective.
We hope this helps bring some clarity to what can be done today to make your environments safer so we can return to productivity. As new products and approaches become available, we will send out a follow up to this document. Please feel free to contact us if we can be of assistance.
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Ross Forry
Service Operations Manager
